(1) Zeolite-its species, mode of occurrence, distribution and condition of formation : Zeolitization is classified into three ; Ca-silicate, Ca-Na-silicate and Na-silicate types. Hydrothermal zeollites which show zonal distribution often occur in geothermal areas in volcanic belts, and are usefl to estimate temperatural and chemical chenges of hydrogthermal activity in such geothermal areas. This study summarized the condition of formation of the zeolites(2) Geochemical study on alteration minerals of basalts in the Furutobe Kuroko mining area : Chlorite (230-250ﾟC) was formed under lower temperature than epidote (250-280ﾟC), based on fluid inclusions. The water/rock ratio of the former (max.40) was lager than that of the latter (0.1-0.8). These should be mainly attributed to porosity of the original basalts(3) Sulfur isotopic study on hydrothermal deposits in the southern Fossa Magna area(4) Ferrierite from Monbertsu, Hokkaido(5) Pavonite from the Ikuno mine, Hyogo Prefecture(6) Semseyite from the Chichibu mine, Saitama Prefecture(7) Mineralization of the Suehiro vein of the Otome mine, Yamanashi Prefecture.(7)山梨県乙女鉱山末広脈の鉱化作用について